Common questions,
straight answers.

Occasional pressure drops (once or twice a year) are normal. If you're repressurising monthly or more, there is a leak in the system. Check all radiator valves and pipe joints for damp patches or white mineral deposits. A failing expansion vessel is another common cause — it causes pressure to spike when hot and drop when cold.

Find the filling loop — usually a braided silver hose with two small valves, located under or near the boiler. Turn both valves to the open position (slot in line with the pipe). Watch the pressure gauge rise. When it reaches 1–1.5 bar, close both valves. Press the boiler reset button. Do this with the boiler cold for best accuracy.

Fault codes are your boiler's way of telling you why it has locked out. Some codes (typically low pressure codes like F22 on Vaillant, E10 on Baxi) are safe to remedy yourself and reset once. Others — fan faults, gas valve faults, overheat lockouts — should not be repeatedly reset. Never reset a boiler more than twice for the same fault.

Trapped air is the answer — almost every time. Air rises in the system and collects at the top of the radiator. The fix takes about 10 minutes: use a radiator bleed key to open the bleed valve at the top corner until water flows out (no more hissing). Afterwards, check your boiler pressure and repressurise if it has dropped.

Remove the cistern lid and watch what's happening. If water is trickling into the pan: press the rubber flap valve at the bottom — if it stops, the flap valve is worn (a £3–£8 part). If water is running into the overflow pipe outside: the fill valve isn't shutting off — try bending the float arm downward slightly.

A dripping tap is almost always a worn washer or cartridge. For traditional pillar taps: it's a rubber washer, which costs pennies. For quarter-turn ceramic taps: the ceramic cartridge has cracked. For single-lever mixer taps: the internal cartridge is worn. All are DIY-friendly if you're comfortable turning off the water supply.

When the system is cold (before the heating has been on), pressure should read between 1 and 1.5 bar. When the heating is running and the system is warm, pressure naturally rises to 1.5–2 bar — this is completely normal. Below 0.5 bar: the boiler may not fire. Above 3 bar: call a Gas Safe engineer.

Act immediately: Do NOT turn any electrical switches on or off. Do NOT use a naked flame. Open windows and doors. Leave the property. Call the National Gas Emergency Service from outside: 0800 111 999 (free, 24/7). Do not return until told it is safe.

Safe DIY: replacing tap washers, bleeding radiators, repressurising the boiler, fixing a running toilet, unblocking a sink. Always use a Gas Safe registered engineer for any gas work — it is illegal to carry out gas work without registration. Unvented cylinder work also requires specialist certification.